UNIVERSITY    OF    CALIFORNIA     AGRICULTURAL   EXPERIMENT  STATION 
COLLEGE   OF  AGRICULTURE  BENJ-  '°E  WHEELER-  "««'"•" 

THOMAS    FORSYTH    HUNT,    DEAN  AND   DIRECTOR 

BERKELEY  h.  e.  van  norman,  vice-director  and  dean 

University  Farm  School 


CIRCULAR  No.  212 
April,  1919 

SALVAGING  RAIN-DAMAGED  PRUNES 

By  W.  V.  CRUESS 


A.     RAIN   DAMAGE,    1918 

1.  The  September  Rains. — The  heavy  and  unexpected  rains  of 
September  came  at  a  time  when  most  of  the  prune  crop  was  either  on 
trays  or  still  in  the  orchard.  Only  a  small  part  of  the  crop  had  been 
dried  and  placed  under  cover.  The  storm  began  September  12,  about 
dusk,  and  rain  fell  almost  daily  for  over  two  weeks.  For  about  three 
weeks,  following  September  12,  the  weather  was  cloudy,  moist,  and 
warm,  unfavorable  to  drying,  and  very  favorable  to  the  development 
of  mold  and  fermentation.  A  large  part  of  the  crop  was  a  complete 
loss.  Some  of  the  fruit  was  finally  dried  but  sold  at  a  reduced  price 
because  of  inferior  quality.  A  relatively  small  portion  of  the  crop 
made  first  grade  dried  fruit. 

As  most  growers  expected  the  storm  to  last  but  a  day  or  two, 
little  was  done  during  the  first  few  days  that  would  protect  the  prunes 
through  a  long  period  of  wet  weather.  Most  of  the  prunes  were  finally 
stacked,  but  many  were  wet  before  stacking.  After  four  days  of 
rainy  weather,  many  of  the  prunes  had  become  so  moldy  that  little 
could  be  done  to  save  them  in  the  short  time  available  before  they 
spoiled  completely.  To  make  conditions  worse,  labor  was  very  scarce 
and  often  of  inferior  quality. 

In  spite  of  these  adverse  conditions,  certain  dry-yards  were  able 
to  save  a  considerable  portion  of  their  fruit  by  use  of  the  methods 
to  be  described  later. 

2.  Extent  of  the  Damage. — It  is  difficult  to  estimate  accurately  at 
this  time  (January  1,  1919)  the  total  loss  to  the  prune  industry, 
because  all  of  the  salable  fruit  has  not  yet  reached  the  packers  and 
considerable  fruit  in  packing  houses  has  been  condemned  by  the  pure 
food  authorities.  Most  of  the  fruit  in  the  orchards  at  the  time  of  the 
rain  was  lost  and  at  least  25  per  cent  of  that  in  the  yards  was  a  total 
loss.    These  two  items  represent  about  50  per  cent  of  the  crop.     The 


money  loss  was  greater  than  this  because  the  remaining  50  per  cent 
brought  a  lower  price  than  would  normally  be  the  case,  and  the  cost 
of  production  was  increased  because  of  labor  and  material  spent  in 
attempts  at  salvage. 

It  is  probable  that  the  money  loss  would  represent  60  per  cent  of 
the  value  of  the  entire  crop  or  at  least  $5,000,000. 

3.  Nature  of  the  Damage. — Most  of  the  damage  was  caused  by  mold 
growth  and  yeast  fermentation.  Injury  resulted  also  from  splitting 
of  fruit  in  the  orchard  and  softening  of  the  fruit  both  in  the  orchard 
and  on  the  trays. 


Fig.  1. — A  Santa  Clara  Valley  dry-yard  shortly  after  the  rain.     Trays  are  elevated 
at  an  angle  to  keep  them  off  the  wet  ground. 


(a)  Molding:  Three  days  after  the  rain  began,  mold  growth  was 
visible  on  much  of  the  fruit  on  the  trays.  Within  a  week  it  was 
difficult  to  find  any  untreated  fruit  free  from  mold. 

Four  forms  of  mold  predominated,  although  many  other  types  were 
present.  A  greenish  brown  mold  grew  on  the  exposed  surfaces  of 
the  fruit  on  the  trays.  To  the  eye  it  appeared  as  a  short  ' '  fuzzy ' '  and 
often  powdery  growth.  The  microscope  showed  it  to  be  an  Altemaria. 
It  did  not  affect  the  flavor  of  the  fruit  but  seemed  to  cause  loss  of 
sugar. 

A  black  pustule-like  growth  of  "sooty  mold"  was  very  common. 
It  was  found  to  consist  of  a  mixture  of  cells  and  filaments  in  which 
large  yeast-like  cells  predominated.     The  flavor  of  the  prunes  seemed 


little  injured  by  its  presence,  but  the  skin  of  the  fruit  was  softened 
and  the  appearance  badly  damaged. 

A  cottony  growth  of  white  mold  filaments  often  covered  all  of  the 
fruit  on  the  trays  and  filled  the  spaces  between  the  fruit.  It  was 
found  to  be  a  form  of  Mucor,  which  did  not  noticeably  affect  the  flavor 
of  the  fruit.    Its  appearance  is  shown  in  figure  2. 

The  most  damaging  mold  consisted  of  ordinary  green  Pencillium. 
It  grew  most  commonly  on  the  under  side  and  edges  of  the  fruit  in 
contact  with  the  tray  and  also  on  the  upper  surface  of  wet  trays.  The 
skin  of  the  fruit  was  softened  rapidly,  separated  from  the  fruit,  and 


Fig.  2. — Mucor  mold  growing  on  wet  prunes.     September  20,  1918. 

stuck  to  the  trays  when  the  mold  had  been  growing  several  days.  It 
penetrated  the  fruit  and  imparted  a  disgusting  moldy  odor  and  flavor. 
Trays  were  badly  injured  and  must  be  thoroughly  cleaned  before 
being  used  another  season. 

Even  after  thorough  processing,  fruit  that  has  become  very  moldy 
on  the  trays  can  be  recognized  by  the  microscope.  To  examine  the 
fruit  for  mold,  scrape  a  little  of  the  surface  with  a  knife,  mount  the 
material  obtained  on  a  slide  and  examine  with  the  microscope. 

(&)  Fermentation:  Fermentation  of  the  fruit  became  evident 
about  three  days  after  the  start  of  mold  growth.  Most  of  the  fruit 
that  had  not  received  preventive  treatment  was  by  September  20  in 
active  fermentation.    Fermentation  was  caused  by  yeast  which  appar- 


entry  first  developed  around  the  pit.  It  probably  gained  entrance 
through  the  stem  end  and  in  a  very  short  time  the  whole  flesh  of  the 
fruit  became  filled  with  yeast  cells.  The  fruit  swelled  through  the 
formation  of  carbon  dioxide  gas  and  developed  a  strong  alcoholic 
flavor.  The  fruit  lost  a  great  deal  of  sugar  by  this  fermentation.  The 
alcohol  evaporated  as  the  fruit  became  dry.  The  presence  of  gas 
pockets  around  the  pit  and  in  the  flesh  of  the  dried  fruit  is  the  most 
visible  evidence  in  the  dried  fruit  that  fermentation  has  taken  place. 
Prunes  dried  after  severe  alcoholic  fermentation  are  practically 
nothing  but  ' '  skin  and  pit ' ' ;  very  little  sugar  is  left.  Such  fruit  is 
light  and  will  float  in  water  if  tested  soon  after  drying. 

The  flesh  of  fermented  prunes  examined  under  the  microscope 
shows  large  numbers  of  yeast  cells.  This  is  a  sure  method  of  differ- 
entiating between  sound  and  fermented  fruit.  When  fermentation 
does  not  progress  very  far,  the  fruit  contains  almost  as  much  sugar 
as  sound  fruit  and  when  cooked  is  probably  just  as  wholesome  as 
fruit  which  has  not  been  attacked  by  yeast. 

(c)  Vinegar  Fly  Larvae:  The  soft  fermenting  fruit  attracted 
vinegar  flies.  The  eggs  of  these  flies  were  deposited  on  the  fruit  and 
within  about  ten  days  after  the  beginning  of  the  rain,  much  of  the 
fruit  was  infested  with  their  maggots  (larvae).  Such  fruit,  of  course, 
became  worthless. 

(d)  Mechanical  Damage  to  Fruit  on  Trays:  The  rain  softened 
the  fruit  very  badly  in  many  cases  so  that  it  flattened  or  stuck  to  the 
trays.    Such  fruit  had  to  be  removed  by  hand  sorting  after  drying. 

It  was  also  claimed  that  fruit  exposed  to  the  rains  for  several  days 
lost  a  great  deal  of  sugar  by  leaching.  It  was  difficult,  however,  to 
ascertain  how  much  sugar  was  lost  in  this  way  because  such  fruit 
usually  fermented  or  molded. 

(e)  Damage  to  Fruit  in  Orchard:  For  four  or  five  days  after 
the  beginning  of  the  storm,  the  fruit  on  the  trees  and  ground  appeared 
sound,  although  a  great  deal  of  it  had  cracked.  "Within  a  week  much 
of  this  fruit  was  severely  attacked  with  a  greenish  brown  mold 
(Alternaria)  and  common  green  penicillium  mold.  Besides  this  very 
evident  injury,  the  fruit  became  excessively  soft  and  " mushed"  down 
badly  in  dipping.  Attempts  to  dry  it  without  dipping  were  not  satis- 
factory because  of  the  slowness  of  drying  and  the  development  of  large 
numbers  of  "frogs." 

Because  the  orchard  ground  was  so  soft  after  the  rain  and  because 
the  fruit  in  the  yards  demanded  so  much  attention,  much  of  the  fruit 
in  the  orchards  became  worthless  before  the  growers  had  an  oppor- 
tunity to  gather  it.     On  September  18,  the  fruit  on  the  trees  and  on 


the  ground  was  examined  and  from  25  to  50  per  cent  was  found  to 
be  sound;  the  remaining  75  or  50  per  cent  was  cracked  badly  and 
more  or  less  moldy.  Practically  all  of  the  fruit  was  too  soft  to  be 
handled  satisfactorily  by  the  usual  methods.  On  September  21, 
orchards  in  the  same  locality  were  examined  and  not  over  5  per  cent 
of  the  fruit  was  found  to  be  whole  and  sound. 

B.     TREATMENT  OF  FRUIT  WITH   ORDINARY   DRY-YARD   EQUIPMENT 

1.  Stacking  the  Trays. — Most  fruit  in  the  dry-yards  was  stacked  as 
soon  as  possible  after  the  rain  started,  but  much  of  it  became  wet 
before  stacking  and  a  great  deal  more  became  wet  in  the  stack  because 
the  rain  was  so  severe  and  so  prolonged.  The  rain  was  too  heavy  and 
prolonged  for  stacking  to  accomplish  much  good. 

2.  Turning  Fruit  on  Trays. — After  a  light  rain,  molding  can  be 
checked  and  drying  facilitated  by  turning  or  stirring  the  fruit  on  the 
trays.  This  treatment  was  of  very  little  benefit  in  September,  because 
of  the  moist  atmosphere  and  frequent  rains. 

3.  Elevating  Trays  above  Ground. — Wet  ground  tends  to  impede 
the  drying  of  fruit  on  trays  in  contact  with  the  ground.  The  trays 
were  raised  from  the  ground  in  most  yards  as  shown  in  figure  1,  but 
this  practice  did  not  materially  assist  drying  because  of  the  long- 
continued  unfavorable  weather. 

4.  Transfer  to  Dry  Trays. — Where  empty  dry  trays  were  available, 
the  transfer  of  wet  fruit  to  these  was  an  important  factor  in  saving 
some  fruit  that  was  already  at  least  two-thirds  dried.  Most  yards  had 
no  extra  trays. 

5.  Dipping  Fruit  from  Trays. — Mold  that  has  started  to  develop 
on  prunes  can  be  destroyed  by  dipping  the  fruit  in  boiling  water  or 
a  hot  dilute  solution  of  lye  or  salt.  This  method  was  given  a  thorough 
trial  by  several  yards,  but  the  prolonged  period  of  wet  weather  per- 
mitted mold  to  develop  again  after  dipping.  Moldy  trays  reinfected 
the  fruit  and  as  a  result,  dipping  of  the  fruit  alone  gave  no  positive 
results. 

6.  Sulfuring. — No  single  method  of  treating  the  wet  fruit  proved 
more  effective  than  that  of  exposing  it  for  two  to  three  hours  to  the 
fumes  of  burning  sulfur.  The  University  recommended  this  method 
strongly.  But  even  before  its  recommendation  was  given,  many  yards 
had  already  undertaken  the  sulfuring  of  as  much  of  the  fruit  as  their 
sulfuring  house  capacity  permitted. 

Two  to  three  hours'  sulfuring  killed  all  mold  and  yeast  present 
in  or  on  the  fruit  and  impregnated  the  fruit  with  sufficient  sulfurous 


acid  to  prevent  growth  of  mold  or  yeast,  which  might  infect  the  fruit 
later.  The  sulfured  fruit  dried  much  more  rapidly  than  untreated 
fruit. 

The  main  disadvantages  of  the  sulfuring  of  the  fruit  were  the 
production  of  a  lighter  color,  and  of  a  tart  or  ''plum"  taste  in  the 
finished  product.  Where  the  fruit  was  two-thirds  dry  or  more,  the 
bleaching  effect  of  the  sulfur  was  negligible;  where  freshly  dipped 


Fig.  3. — Common  type  of  sulfur  house  in  use  in  Santa  Clara  Valley. 

prunes  were  sulfured,  the  fruit  after  drying  belonged  to  the  "ruby" 
prune  class.  The  dry-yards  expect  to  receive  a  slightly  lower  price 
for  sulfured  fruit  than  for  perfect  unsulfured  fruit,  but  any  profitable 
return  is  to  be  preferred  to  a  total  loss.  The  dry-yards  did  not  possess 
adequate  equipment  and  did  not  start  their  operations  in  time  to 
treat  any  appreciable  percentage  of  the  crop. 

Should  this  emergency  ever  arise  again,  it  is  advised  with  all 
emphasis  that  the  dry-yards  utilize  their  sulfuring  houses  to  the 
utmost  and  construct  with   all   possible   speed   temporary  sulfuring 


hoods.  These  can  be  built  very  quickly  by  local  mills,  lumber  yards, 
and  carpenters.  All  such  should  be  enlisted  to  turn  out  sulfur  hoods 
in  quantity.  Professor  Bioletti  has  described  such  a  hood  for  raisin 
dry-yards  which  could  be  modified  for  use  with  prunes.  Specifications 
for  this  hood  are  given  in  a  recent  circular.  It  is  made  to  be  placed 
over  two  stacks  of  2  X  3  feet  raisin  trays  and  sulfur  is  burned  in  a 
can  or  pan  between  the  stacks  and  under  the  hood. 

For  8X3  feet  trays,  a  suitable  hood  would  be  9^2  feet  long  by 
40  inches  wide  by  5  feet  high.  It  would  be  built  of  a  light,  braced 
frame  covered  with  light  roofing  paper ;  i.e.,  rubberoid  roofing  or 
building  paper.*  It  would  be  fitted  with  handles  at  each  bottom 
corner  by  which  two  men  could  lift  it  and  set  it  down  over  the  trays. 
It  is  11/2  feet  longer  than  the  trays  and  in  this  space  the  sulfur  may 
be  burned. 

It  would  even  be  a  wise  plan  to  have  a  number  of  these  sulfur  hoods 
made  up  and  stored  in  a  convenient  place,  as  an  insurance  against 
rain  damage  in  future  years.  Their  cost  is  small ;  each  would  not  cost 
more  than  five  dollars  and  would  be  capable  of  saving  over  one  and 
a  half  tons  of  fruit  per  twenty-four  hours.  No  better  investment  for 
a  prune  dry -yard  can  be  made. 

Mr.  F.  R.  Shafter,  of  Stevens  Creek  Road,  San  Jose,  began  sulfur  - 
ing  his  fruit  the  third  day  after  the  rain  had  started.  He  exposed  the 
fruit  in  most  cases  for  about  three  hours  to  the  fumes  of  the  sulfur 
and  then  handled  it  in  the  yard  in  the  usual  way.  He  also  sulfured 
practically  all  fresh  fruit  dipped  after  the  rain.  Fruit  sulfured  after 
it  had  become  moldy  or  fermented  did  not  develop  further  mold  or 
yeast,  but  of  course  the  damage  done  before  the  fruit  was  sulfured 
was  not  removed.  The  sulfured  and  unsulfured  fruit  was  examined 
on  November  29.  The  color  of  the  sulfured  fruit  ranged  from  nearly 
btack  to  "ruby,"  but  was  considerably  lighter  in  color  than  the 
untreated  fruit.  Most  of  it  was  free  from  mold  and  yeast,  and  clean 
in  flavor.  Mr.  Shafter  was  well  pleased  with  the  results  and  would 
repeat  the  treatment  in  another  such  emergency.  He  sold  the  fruit 
at  a  profitable  price. 

Others  who  obtained  good  results  from  sulfuring  were  F.  Holmes, 
San  Jose;  A.  E.  Graham,  of  J.  H.  Flickinger  Company,  of  San  Jose; 
Warren  Hyde,  Cupertino;  and  William  Fisher,  Union  Station,  Napa 
County.  Mr.  Hyde  redipped  his  fruit  before  sulfuring.  He  found 
that  sulfuring  checked  all  mold  and  yeast  growth  and  did  not  lighten 
the  color  of  fruit  which  was  half  or  two-thirds  dry  when  sulfured. 

*  Professor  Bioletti  recommends  covering  the  frame  first  with  burlap  to  give 
rigidity.    Then  this  is  covered  with  building  paper  to  make  the  hood  fume-tight. 


8 

7.  Treatment  of  Fruit  from  the  Orchard. — As  already  stated,  the 
fruit  on  the  trees  and  ground  became  soft  after  the  rain.  Attempts 
to  dry  this  fruit  without  dipping  were  not  satisfactory  and  dipping 
resulted  in  much  breaking  or  " mushing' '  of  the  fruit.  Fruit  which 
was  not  sulfured  molded  in  most  cases. 

Therefore,  the  most  practical  method  of  handling  the  fruit  is  to 
gather  only  the  best  fruit  in  the  orchard  and  to  leave  the  excessively 
soft  and  badly  damaged  fruit.  This  selected  fruit  can  then  be  given 
a  short  dip  and  spread  carefully  on  trays.  To  prevent  development 
of  mold  or  yeast,  it  should  be  sulfured  for  two  hours  and  then  dried 
in  the  usual  manner. 

The  experiences  of  many  dry-yards  during  the  past  season  have 
shown  this  method  to  be  satisfactory. 

8.  General  Application  of  Evaporators  to  the  Drying  of  Damaged 
Prunes. — Evaporators  may  be  used  in  one  of  several  ways.  The  wet 
fruit  may  be  dried  in  the  evaporator  until  dry  enough  for  packing. 
If  time  is  available,  this  is  probably  the  best  procedure. 

Or,  the  fruit  and  trays  may  be  dried  a  few  hours  in  the  evaporator 
to  remove  surface  moisture  only.  Drying  would  then  be  completed 
in  the  sun. 

It  is  also  feasible  to  sulfur  lightly  the  fruit  which  can  not  be  put 
in  the  evaporator  at  once  and  this  fruit  can  then  be  dried  later.  This 
was  done  by  William  Fisher  of  Union  Station,  Napa  County,  with 
excellent  results. 

9.  Sorting  Damaged  Fruit. — Most  of  the  fruit  was  left  on  the  trays 
and  allowed  to  dry  regardless  of  mold  or  fermentation.  Much  of  this 
fruit  was  of  fair  quality  when  dry,  but  was  mixed  with  a  large  per- 
centage of  moldy  or  fermented  fruit  and  "slabs."  Some  dry-yards 
attempted  to  hand  sort  this  material.  It  is  doubtful  whether  they 
were  repaid  for  the  expense  and  trouble  incurred. 

It  was  found  by  experiments  at  the  University  that  badly  fer- 
mented fruit  would  float  on  water  and  that  the  sound  fruit  would 
sink.  This  gave  an  easy  method  of  separation.  The  use  of  a  5  per  cent 
salt  solution  (6%  ounces  of  salt  per  gallon  of  water)  gave  a  much 
sharper  separation  than  water.  A  10  per  cent  solution  of  glucose, 
corn  syrup,  or  sugar  gave  as  good  a  separation  as  a  5  per  cent  brine 
and  in  addition  gave  a  finished  gloss  to  the  fruit. 

A  typical  lot  of  damaged  fruit  yielded  40  per  cent  fermented 
material  and  60  per  cent  sound  fruit  by  this  method.  The  "slabs" 
sank  with  the  sound  fruit,  but  were  easily  recognized  and  separated 
in  subsequent  hand  sorting. 


The  ordinary  dipping  basket  and  dipping  tank  could  be  used.  The 
fermented  prunes  would  rise  to  the  surface  and  could  be  skimmed  off ; 
the  sound  fruit  would  remain  in  the  basket  and  could  be  dumped 
from  the  basket  on  to  clean  dry  trays  where  the  surface  of  the  prunes 
could  be  dried  before  delivery  to  the  packing  house.  This  method 
does  not  give  good  results  with  fruit  which  has  been  held  a  month 
or  more  after  it  is  dry. 

C.      UTILIZATION    OF    BADLY    DAMAGED    PRUNES 

1.  Value  for  Alcohol. — Analyses  and  fermentation  tests  made  by 
Mrs.  Jean  Christie  in  the  Zymology  Laboratory  showed  that  one  ton 
of  damaged  prunes  could  be  made  to  yield  twenty  to  fifty  gallons 
of  95  per  cent  alcohol.  At  50  cents  per  gallon,  this  has  a  value  of  $10 
to  $25  per  ton  of  partially  dried  fruit  as  received.  This  is  not  a  large 
money  return. 

Alcohol  distilleries  use  cheap  beet  molasses  and  were  not  interested 
in  the  possible  utilization  of  prunes  for  alcohol  for  powder  manu- 
facture when  prospects  of  the  end  of  the  war  came. 

2.  Value  for  Vinegar. — On  the  basis  of  a  distilled  vinegar  of  10  per 
cent  acetic  acid  content,  one  ton  of  the  damaged  friut  would  yield 
200  to  500  gallons  of  vinegar.  At  15  cents  per  gallon,  this  would 
bring  a  return  of  $30  to  $75  per  ton  of  fruit.  The  demand  for  vinegar 
is  limited  and  it  is  therefore  doubtful  if  any  appreciable  quantities  of 
fruit  could  be  used  in  this  way. 

3.  Syrup. — A  palatable,  clear,  dark  amber  syrup  was  made  from 
the  damaged  fruit  on  a  laboratory  scale.  Many  different  methods 
were  tested,  but  the  following  was  found  most  satisfactory. 

The  prunes  were  heated  to  between  180°  and  190°  F.  with  twice 
their  weight  of  water.  The  mixture  after  heating  was  left  twenty-four 
hours.  The  fruit  was  then  placed  in  a  cider  press  between  heavy  press 
clotlfc  and  subjected  to  hydraulic  pressure  of  about  500  pounds  per 
square  inch.  The  resulting  juice  was  analyzed  for  its  acid  content 
and  enough  precipitated  chalk  added  to  reduce  the  acidity  to  .2  per 
cent.  To  the  juice  was  then  added  2  per  cent  by  weight  of  "Filter- 
ed" to  aid  in  filtration.    The  treated  juice  filtered  fairly  well. 

The  clear  juice  so  obtained  contained  about  15  per  cent  of  sugar 
(15  per  cent  Balling  test)  and  .2  per  cent  acid.  It  was  then  concen- 
trated in  a  vacuum  kettle  to  from  65  per  cent  to  70  per  cent  Balling. 

One  ton  of  the  prunes  of  the  sort  used  in  the  experiment  would 
give  by  this  method  about  fifty  gallons  of  syrup.  At  75  cents  per 
gallon,  its  value  would  be  about  $35. 


10 

4.  Pits. — The  prunes  examined  contained  from  13  per  cent  to 
20  per  cent  of  pits.  The  kernels  were  equal  to  18  per  cent  of  the 
weight  of  the  pits.  The  kernels  were  rich  in  oil  and  bitter  almond  oil. 
It  is  probable  that  the  pits  would  afford  a  fairly  valuable  by-product. 
They  can  be  separated  from  the  pulp  by  a  machine  similar  to  a  tomato 
pulper. 

5.  Canwmg. — The  badly  damaged  prunes  are  not  suitable  for  can- 
ning because  the  State  Food  and  Drug  Laboratory  does  not  consider 
them  fit  for  food  as  prunes.  The  fruit  can,  however,  be  carefully 
sorted  and  the  better  material  canned  in  a  light  sugar  syrup.  The 
fruit  may  be  cooked  before  canning  or  the  cans  may  be  filled  about 
half  full,  syrup  added,  and  the  fruit  cooked  in  the  sealed  can.  This 
method  should  also  form  a  good  outlet  for  small  prunes  in  normal 
years. 

6.  Jams  and  Butters. — These  products  were  suggested  by  several 
manufacturers  and  others.  Badly  damaged  fruit  can  not  be  used  for 
these  products,  even  if  the  products  can  be  made  to  possess  a  pleasing 
flavor,  because  the  molds  and  yeasts  will  be  present  in  the  finished 
product  and  will  readily  be  found  by  use  of  the  microscope.  The 
State  Board  of  Health  would  therefore  rightly  condemn  all  products 
of  this  sort  unless  they  were  made  from  sound  clean  fruit. 

7.  Value  for  Hog  Feed. — Under  Professor  Jaffa's  direction,  the 
feeding  of  damaged  prunes  for  garbage  fed  hogs  was  tested  by  W.  L. 
Bohannon.  Excellent  results  were  obtained  by  using  85  per  cent 
garbage  and  15  per  cent  prunes.  The  hogs  ate  the  prune  flesh  and 
then  cracked  the  pits  to  obtain  the  kernels.  Gains  in  weight  were 
rapid.  Santa  Clara  Valley  hog  feeders  also  obtained  good  results  in 
the  way  of  gains  but  found  that  the  hogs  must  be  finished  on  grain 
feed  to  avoid  disagreeable  color  and  flavor  in  the  pork,  which  result  if 
large  proportions  of  prunes  are  fed.  Where  they  form  only  15  per 
cent  of  the  ration,  this  defect  would  probably  not  result. 


11 


SUMMARY 


1.  The  September  rains  of  1918  destroyed  at  least  50  per  cent  of 
the  value  of  the  prune  crop  and  caused  a  loss  of  probably  not  less 
than  $5,000,000. 

2.  Most  of  this  damage  was  caused  by  mold  growth  and  yeast 
fermentation  during  the  long  period  of  warm  damp  weather  following 
the  rain. 

3.  Usual  methods  of  handling  the  fruit  by  stacking  the  trays, 
turning  the  fruit  on  the  trays,  redipping,  etc.,  failed  to  check  the  mold 
and  yeast  in  most  cases. 

4.  Sulfuring  the  fruit  on  the  trays  for  two  to  three  hours,  as  is 
done  with  apricots,  checked  mold  and  yeast  growth  and  made  it 
possible  to  dry  the  fruit  without  artificial  heat.  Fruit  dried  in  this 
way  was  salable  and  of  excellent  flavor ;  it  was  usually  lighter  in  color 
than  fruit  dried  in  the  usual  way. 

5.  Fermented  dried  prunes,  if  not  held  too  long  after  drying,  may 
be  separated  from  sound  fruit  by  flotation  in  water,  or,  better,  in  a 
5  per  cent  salt  solution  or  10  per  cent  glucose  solution.  This  process 
simplifies  sorting  after  drying. 

6.  Analyses  of  damaged  fruit  and  investigations  of  its  utilization 
for  alcohol,  acetic  acid,  vinegar,  and  syrup  manufacture  were  made. 
It  was  also  tested  in  a  practical  way  as  a  hog  feed  by  Professor  Jaffa. 
Results  were  fairly  satisfactory,  but  returns  in  no  case  would  be 
very  large. 

CONCLUSIONS    AND    RECOMMENDATIONS 

1.  Exposure  of  wet  prunes  to  the  fumes  of  burning  sulfur  for  two 
to  three  hours  is  the  most  simple  and  effective  method  of  quickly 
checking  molding  and  fermentation.  Sulfuring  should  not  be  delayed 
more  than  three  days  after  the  rain.  Every  prune  dry-yard  should 
have  adequate  sulfur  house  capacity  for  such  an  emergency  as  that 
of  September,  1918. 

2.  Usual  methods  of  handling  wet  prunes  by  turning,  stacking, 
etc.,  are  not  sufficient  under  the  conditions  of  the  1918  season.  Sul- 
furing or  artificial  evaporation  are  necessary. 

3.  More  evaporators  should  be  built  and  kept  in  repair  for  imme- 
diate use. 

4.  Badly  damaged  fruit  should  not  be  thrown  away  but  should  be 
utilized  for  hog  feed,  syrup,  or  in  some  other  way. 


STATION  PUBLICATIONS  AVAILABLE   FOR   FREE   DISTRIBUTION 


No. 

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271. 
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277. 


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148. 
151. 
152. 

153. 

154. 

155. 
156. 
157. 
158. 
160. 
162. 

164. 
165. 

166. 


Enological   Investigations. 

Humus  in  California  Soils. 

The  Loquat. 

Utilization  of  the  Nitrogen  and  Organic 
Matter  in  Septic  and  Imhoff  Tank 
Sludges. 

Deterioration  of  Lumber. 

Irrigation  and  Soil  Conditions  in  the 
Sierra  Nevada  Foothills,  California. 

The  Citricola  Scale. 

New  Dosage  Tables. 

Melaxuma  of  the  Walnut,  "Juglans 
regia." 

Citrus  Diseases  of  Florida  and  Cuba 
Compared  with  Those  of  California. 

Size  Grades  for  Ripe  Olives. 

The  Calibration  of  the  Leakage  Meter. 

A  Spotting  of  Citrus  Fruits  Due  to  the 
Action  of  Oil  Liberated  from  the  Rind. 

Experiments  with  Stocks  for  Citrus. 

Growing  and  Grafting  Olive  Seedlings. 

A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

Feeding  Dairy  Calves  in  California. 

Commercial  Fertilizers. 

Preliminary  Report  on  Kearney  Vine- 
yard Experimental  Drain. 

The  Common  Honey  Bee  as  an  Agent 
in  Prune  Pollination. 

The  Cultivation  of  Belladonna  in  Cali- 
fornia. 

The  Pomegranate. 

Sudan  Grass. 


BULLETINS 

No. 

278. 

279. 

280. 


281. 

282. 

283. 
284. 
285. 
286. 
288. 

290. 

292. 

293. 
296. 
297. 
298. 
299. 

300. 
301. 

302. 

303. 
304. 

305. 


Increasing  the  Duty  of  Water. 

Grafting  Vinifera  Vineyards. 

The  Selection  and  Cost  of  a  Small 
Pumping  Plant. 

Alfalfa  Silage  for  Fattening  Steers. 

Spraying  for  the  Grape  Leaf  Hopper 

House  Fumigation. 

Insecticide  Formulas. 

The  Control  of  Citrus  Insects. 

Spraying  for  Control  of  Walnut  Aphis. 

County  Farm  Adviser. 

Official  Tests  of  Dairy  Cows. 

Melilotus  Indica. 

Wood  Decay  in  Orchard  Trees. 

The  Silo  in  California  Agriculture. 

The  Generation  of  Hydrocyanic  Acid 
Gas  in  Fumigation  by  Portable  Ma- 
chines. 

The  Practical  Application  of  Improved 
Methods  of  Fermentation  in  Califor- 
nia Wineries  during  1913  and  1914. 

Practical  and  Inexpensive  Poultry  Ap- 
pliances. 

Control  of  Grasshoppers  in  Imperial 
Valley. 

Oidium  or  Powdery  Mildew  of  the  Vine. 

Tomato  Growing  in  California. 

"Lungworms." 

Feeding  and  Management  of  Hogs. 

Some  Observations  on  the  Bulk  Hand- 
ling  of    Grain    in    California. 

Announcement  of  the  California  State 
Dairy  Cow  Competition,   1916-18. 

Irrigation  Practice  in  Growing  Small 
Fruits  in  California. 

Bovine  Tuberculosis. 

How    to    operate    an    Incubator. 

Control  of  the  Pear  Scab. 

Home  and  Farm  Canning. 

Lettuce  Growing  in  California. 

White  Diarrhoea  and  Coccidiosis  of 
Chicks. 

Small  Fruit  Culture  in  California. 

Fundamentals  of  Sugar  Beet  Culture 
under  California  Conditions. 

The  County  Farm  Bureau. 


CIRCULARS 
No. 
167. 
168. 


169. 
170 


172. 
173 


174 
175. 


176 


177. 
179 


182. 

183. 

184. 
186. 
187. 
188. 
189. 
190. 
191 
193. 
195, 

197. 

198. 
200. 

201. 
202. 

203. 
204. 

205. 
206. 
207. 


Grain  Sorghums. 

Irrigation  of  Rice  in  California. 

Irrigation  of  Alfalfa  in  the  Sacramento 
Valley. 

Control  of  the  Pocket  Gopher  in  Cali- 
fornia. 

Trials  with  California  Silage  Crops  for 
Dairy  Cows. 

The  Olive  Insects  of  California. 

Irrigation  of  Alfalfa  in  Imperial  Valley. 

The  Milch  Goat  in  California. 

Commercial  Fertilizers. 

Potash  from  Tule  and  the  Fertilizer 
Value  of  Certain  Marsh  Plants. 

The  June  Drop  of  Washington  Navel 
Oranges. 

Green  Manure  Crops  in  Southern  Cali- 
fornia. 

Sweet  Sorghums  for  Forage. 

Topping  and  Pinching  Vines. 

The  Almond  in  California. 

Seedless  Raisin  Grapes. 

The  Use  of  Lumber  on  California 
Farms. 

Commercial  Fertilizers. 

California  State  Dairy  Cow  Competi- 
tion,   1916-18. 

Control  of  Ground  Squirrels  by  the 
Fumigation  Method. 

Grape  Syrup. 

A  Study  of  the  Effects  of  Freezes  on 
Citrus  in  California. 

The  Influence  of  Barley  on  the  Milk 
Secretions  of  Cows. 


Feeding    Stuffs    of    Minor   Importance. 
Spraying   for  the  Control  of  Wild  Morn- 

ing-Glory  within  the  Fog  Belt. 
The    1918   Grain  Crop. 
Fertilizing     California     Soils     for    the 

1918   Crop. 
Wheat  Culture. 
The    Construction    of   the   Wood-Hoop 

Silo. 
Farm  Drainage  Methods. 
Progress  Report  on  the  Marketing  and 

Distribution    of    Milk. 
Hog     Cholera      Prevention      and     the 

Serum   Treatment. 
Grain  Sorghums. 
Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial   Count. 
Control     of     the     California     Ground 

Squirrel. 
Extending  the  Area  of  Irrigated  Wheat 

in    California    for    1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of   Sheep  on  the  Farm. 
Poultry  on  the  Farm. 
Utilizing  the  Sorghums. 
Lambing  Sheds. 
Winter    Foraee    Crops. 
Agriculture  Clubs  in  California. 
Pruning  the  Seedless  Grapes. 
A    Study   of   Farm  Labor  in  California. 
Revised  Compatibility  Chart  of  Insecti- 
cides and  Fungicides. 
Suggestions    for    Increasing   Egg   Pro- 
duction  in  a  Time  of  High-Feed  Prices. 
Syrup  from   Sweet  Sorghum. 
Growing  the   Fall   or   Second   Crop  of 

Potatoes  in  California. 
Helpful    Hints   to    Hog   Raisers. 
County    Organization    for    Rural    Fire 

Control. 
Pont   as  a  Manure   Substitute. 
Handbook  of  Plant  Diseases  and  Pest 

Control. 
Blackleg. 
Jack  Cheese. 
Neufchatel  Cheese. 


